This invention relates to an electronic detector for locating metallic objects in a human or animal body, and more particularly to a hand manipulated probe for use by surgeons and the like for locating metal objects hidden from view within a wound or surgical opening.
One of the major difficulties encountered by surgeons, medical examiners, veterinarians, and the like, is the location of foreign objects which have entered a body or carcass as a result of a wound or surgical procedure. More often than not such objects are metallic (bullets, broken scalpel blades, surgical needles, metallic fragments, etc.), and because of the particular manner in which they entered the body their exact locations cannot be determined simply by observation. In many instances, even when multiple X-Ray studies can demonstrate the location of metallic foreign objects, physically locating, grasping, and removing these foreign objects can be extremely difficult because of limited visibility, limited usability of tactile sensations, and limited range of motion of surgical instruments within certain areas of the body. Moreover, in many cases the urgency of the situation rules out the use of any time-consuming procedures for locating the foreign objects. Consequently there is a critical need for an instrument which can be used quickly and relatively simply to locate foreign metal particles in a wound, surgical opening, or the like.
For example, when a bullet enters a person's body at high speed, it may be deflected several times along different paths once it has entered the body, thus making it extremely difficult to determine where it finally came to rest. For that matter fragments of such an object might be located in different parts of the body, and if not completely removed during a surgical procedure could result in malpractice litigation against the surgeon who was responsible for removing the bullet. Surgeons also face the threat of litigation resulting from the accidental loss of surgical needles in a patient's body or accidental breakage and loss of metal instruments (e.g., the tip of a scalpel blade) during a surgical procedure. It is therefore of primary importance that an instrument be provided which will enable a surgeon rapidly and accurately to detect small metal objects in wounds or surgical openings.
Heretofore efforts have been made to provide metal detecting instruments of the type described and typically such instruments have included an electric coil wound within a probe which can be inserted into an incision or wound. For example, U.S. Pat. Nos. 2,393,717 and 2,442,805 disclose instruments of the type in which the tank coil of one of two oscillators is located in the probe. The outputs of the two oscillators are mixed, amplified, and applied to a speaker, or the like, which under normal conditions produces a low frequency beat note. However, when the probe coil approaches a metallic object in a wound or the like, its inductance is changed and causes an audible and unmistakable change in the normal beat frequency to occur, thereby to denote the presence of the metal object.
In the case of U.S. Pat. Nos. 2,321,355 and 2,321,356, one or more probe coils are connected remote from the probe to corresponding balancing coils. When the circuit is energized, the probe coils create around the outside of the probe a field which, when placed in the vicinity of a metal object in a wound, creates an imbalance in the circuit, and thereby triggers an indicator to denote the presence of the object.
Although not concerned with surgical probes, U.S. Pat. No. 3,546,628 discloses a metal detector of the eddy current killed oscillator variety. In this device the detecting coil is the tank coil of an oscillating tank circuit. The oscillator circuit normally is tuned at a high frequency above the audible range, but when the tank coil is detuned by placing the probe near a metal object, the frequency of the output signal drops to an audible range. U.S. Pat. No. 3,381,217 discloses a device for detecting metal particles in fruit, tobacco, and the like, by using the tank coil of an oscillator to detect metal particles in a manner similar to that described above. However, the device is designed to be fixed in a stationary position adjacent a moving conveyor which advances the fruit or tobacco past the detector.
Other types of detectors are disclosed in U.S. Pat. Nos. 3,460,528, 3,209,245 and 4,068,189, but appear to be less pertinent to this invention than those discussed above.
One of the major disadvantages of prior such probes is that their respective balancing circuits require very careful adjustment each time that the associated instrument is to be employed. In an operating room, for example, if the device is powered by a conventional AC power supply, it must be frequently adjusted to compensate for fluctuations in the voltage supply. In those cases where the detection device utilizes a pair of oscillators to develop a beat frequency, ambient temperature changes also affect the tuning of the reference oscillator and therefore require its adjustment prior to using the instrument. Moreover, since the search coils employed in such prior devices are frequently subjected to shock loading during handling, the tuning of the associated detector circuit frequently must be adjusted to compensate for such disturbances.
The very size of such prior detectors has also been a disadvantage, particularly in those cases where time is of the essence, as for example in the emergency room of a hospital where the need for handling bulk equipment could interfere with proper care of a patient. For the same reasons, the patient's care would be neglected if it were necessary to take the time to calibrate or properly adjust a detector of the type described, prior to being able to use it on a patient.
It is therefore an object of this invention to provide an improved anatomical probe or detector of the type described which is substantially more compact and reliable than prior such probes.
A more specific object of this invention is to provide an improved anatomical probe of the type described which does not have to be tuned or adjusted each time prior to its use on a patient or the like.
A further object of this invention is to provide a small, portable, battery-operated anatomical probe or detector which ideally is tuned only once during its manufacture, and thereafter need not to be readjusted prior to its use, during use, or even after repeated use.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.